Among logo-added two-dimensional codes created by superimposing a two-dimensional code representing information by a distribution pattern of cells and a visible logo image, those consisting of cells of a given lightness or greater lightness superimposed on a logo image of given lightness or lower lightness have already been known (for example, see Patent Literature 1).
Furthermore, those consisting of cells of lightness lower than a given lightness superimposed on the part of a logo image that is of a given lightness or greater lightness and cells of given lightness or greater lightness superimposed on the part of the logo image that is of lightness lower than the given lightness have already been known. Such logo-added two-dimensional codes represent information by a distribution pattern of the cell of a given lightness or greater lightness and the part of the logo image that is of a given lightness or greater lightness, and the cell of a lightness lower than the given lightness and the part of the logo image that is of lightness lower than the given lightness (for example, see Patent Literature 2).
The specification, scope of claims, and drawings of the Patent Literature 1 and 2 are entirely incorporated herein by reference.    Patent Literature 1: Unexamined Japanese Patent Application Kokai Publication No. 2007-287004; and    Patent Literature 2: Unexamined Japanese Patent Application Kokai Publication No. 2008-015642.
Unlike two-dimensional codes consisting of only black and white cells, the aforementioned logo-added two-dimensional codes may not be read correctly under the influence of post-printing processing and/or ambient light.
Furthermore, the aforementioned logo-added tow-dimensional codes utilize the cells of a uniform size. Therefore, a problem arises that the design integrity of the logo image will be impaired as the cell size is increased, and the readability of information represented by the logo-added two-dimensional code will be impaired as the cell size is decreased.
Furthermore, in the aforementioned logo-added two-dimensional codes, either the cells of a lightness lower than a given lightness or the cells of a given lightness or greater lightness are alone superimposed on the part of a logo image that can be read as “0” or “1” depending on the influence of post-printing treatment and/or ambient light. Therefore, the information may not be read correctly.
The present invention is invented to solve the above problems and an exemplary object of the present invention is to provide a logo-added two-dimensional code that can be read correctly, and a logo-added two-dimensional code creation device, logo-added two-dimensional code creation method, and program for creating the logo-added two-dimensional code.